Locking polyaxial ball and socket fastener

ABSTRACT

The fastening system consists of the polyaxial ball and socket joint used in conjunction with a bone screw having threads on one end for use in anchoring to the spine and a spherical connector on the other end operating as a pivot point about which a connecting assembly moves in a polyaxial fashion. A substantially U-shaped connecting assembly has a lower receptacle that operates as a socket for housing an upper retainer ring and a lower split retaining ring. The socket is receptive to the spherical connector which is inserted through the lower split retainer ring causing a momentary displacement thereof which allows for the positioning of the spherical connector between the upper and lower retainer rings. A resilient component positioned between the upper retainer ring and the connecting assembly permits relative predetermined placement and retention of the spherical connector relative to the connector assembly due to the force generated by the resilient component and frictional engagement between the surfaces of spherical connector, the upper and lower retainer rings and the connector assembly. The polyaxial ball and socket can be locked into a fixed position.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/355,145, filed on Jan. 9, 2010, entitled “LOCKING POLYAXIALBALL AND SOCKET FASTENER”, which in turn claims the benefit of thefiling date of U.S. Provisional Patent Application No. 61/114,515, filedon Nov. 14, 2008, the contents of which are herein incorporated byreference.

FIELD OF THE INVENTION

This invention is directed to the field of ball and socket fasteners,and in particular to a polyaxial ball and socket fastener adapted foruse as a spinal implant.

BACKGROUND OF THE INVENTION

There are numerous ball and socket fasteners, however, when theapplication is applied to a particular product, the ball and socket mustmeet minimum specifications in order to be effective. For instance, inthe field of spinal pathologies, the development of spinal fixationdevices represents a major medical breakthrough. Surgically implantedfixation systems are commonly used to correct a variety of backstructure problems, including those which occur as a result of trauma orimproper development during growth. A commonly applied fixation systemincludes the use of one or more stabilizing rods aligned in a desiredorientation with respect to a patient's spine. Anchoring screws areinserted into the patient's spinal bones, and a series of connectors areused to rigidly link the rods and anchors.

A variety of designs exist, with each design addressing various aspectsof the difficulties that arise when one re-shapes an individual's spineto follow a preferred curvature. Known spinal implant systems oftencorrect one set of problems only to create new ones.

Common to all spinal implant systems is the necessity for properanchoring to the bone so as to provide support for the aforementionedcomponents. While bone screws are commonly used for anchoring, the useof a polyaxial design has proven very effective in allowing a surgeonthe flexibility to secure an installation with minimal strain on theindividual.

For this and other reasons, screws located in bone structure typicallyuse a polyaxial base and a specially designed connector member forattachment to a component such as an alignment rod. A problem with thecurrent technology is that bone structure cannot be determined until thepatient's bone is exposed. This problem requires a large inventory ofvarious sized implants to be on hand during every surgery. The surgeonmust search through the inventory to assembly a combination based on hisprediction of what will be required. Even if an implant combination ispredicted, the anchoring screw may still require angular insertion dueto muscle structure or nerve locations. Any movement of muscle and othertissue increases the difficulty of the operation and can be a majortrauma to the patient. Still yet, bone condition may require oversizethreads to achieve a suitable purchase to the bone. As a consequence,the surgeon must either maintain a large inventory of anchoring devices,or have a vendor standing by with a large inventory of anchoring devicesthat will hopefully meet the individual requirements.

Common to all spinal implant systems is the necessity for properanchoring to the bone so as to provide support for the aforementionedcomponents. The use of a polyaxial design pedicle screw has proven veryeffective in allowing a surgeon the flexibility to secure aninstallation with minimal strain on the individual. However, one of theproblems with a polyaxial pedicle screw is the lack of a stabilizedangular placement position during installation. Once a polyaxial pediclescrew is inserted into the bone, the connector component portion has yetto receive a connecting rod leaving the connector assembly to flop overmaking it difficult for the Surgeon to grasp while in the midst ofsurgery. This problem is compounded by the need to align multiplecomponent heads for receipt of a connecting rod.

U.S. Pat. No. 7,066,937 discloses an apparatus including a housinghaving a first passage configured to receive a longitudinal member and asecond passage with an axis transverse to the first passage; a fastenerextending through an opening in the housing and being moveable relativeto the housing; the second passage of the housing having an indentation,the indentation including an axially extending surface at leastpartially defining the second passage and an upper surface extendingtransverse to the axially extending surface, a spacer received in thesecond passage of the housing, the spacer having a radial surface belowthe upper surface of the indentation; and a member contacting the uppersurface of the indentation and the radial surface of the spacer thatapplies an axial force to the spacer to prevent relative movementbetween the fastener and the housing and holding the fastener in any oneof a plurality of angular positions relative to the housing.

U.S. Pat. No. 6,485,491 discloses a multi-axial bone anchor assemblythat includes a saddle member, a bone anchoring member and a washer. Thesaddle has a channel that receives a rod. A snap ring secures the washerin the saddle member. The snap ring engages a snap ring recess. Thedisclosed structure would not prevent relative movement between afastener and a housing and would not hold a longitudinal axis of thefastener in any one of a plurality of desired angular positions relativeto a longitudinal of a passage in the housing when a rod, longitudinalmember, is disengaged from a spacer. The patent does not teach anarrangement where a spacer necessarily engages a fastener when a rod,longitudinal member, is so disengaged.

A conventional polyaxial bone screw typically consists of a single shaftwith a coarse thread at one end for threading into the bone. A sphericalball is positioned at an opposite end for coupling to a connectingmember. For example, a number of patents exist for bone screw anchoringassemblies that include a U-shaped connector element which acts as asaddle for attachment to an alignment rod. U.S. Pat. No. 5,133,717 setsforth a sacral screw with a saddle support. Disclosed is the use of anauxiliary angled screw to provide the necessary support in placing thescrew in an angular position for improved anchoring.

U.S. Pat. No. 5,129,900 sets forth an attachment screw and connectormember that is adjustably fastened to an alignment rod. An oblong areaprovided within each connector member allows minute displacement of thealignment rod.

U.S. Pat. No. 4,887,595 discloses a screw that has a first externallythreaded portion for engagement with the bone and a second externallythreaded portion for engagement with a locking nut. The disclosureillustrates the use of a singular fixed shaft.

U.S. Pat. No. 4,946,458 discloses a screw which employs a sphericalportion which is adapted to receive a locking pin so as to allow oneportion of the screw to rotate around the spherical portion. A problemwith the screw is the need for the locking pin and the inability of thebase screw to accommodate a threaded extension bolt.

U.S. Pat. No. 5,002,542 discloses a screw clamp wherein two horizontallydisposed sections are adapted to receive the head of a pedicle screw foruse in combination with a hook which holds a support rod at anadjustable distance.

U.S. Pat. No. 4,854,304 discloses the use of a screw with a top portionthat is adaptable for use with a specially designed alignment rod topermit compression as well as distraction.

U.S. Pat. No. 4,887,596 discloses a pedicle screw for use in coupling analignment rod to the spine wherein the screw includes a clamp permittingadjustment of the angle between the alignment rod and the screw.

U.S. Pat. No. 4,836,196 discloses a screw with an upper portion designedfor threadingly engaging a semi-spherical cup for use with a speciallydesigned alignment rod. The alignment rod includes spaced apartcovertures for receipt of a spherical disc allowing a support rod to beplaced at angular positions.

U.S. Pat. No. 5,800,435 sets forth a modular spinal plate assembly foruse with polyaxial pedicle screw implant devices. The device includescompressible components that cooperatively lock the device alongincluded rails.

U.S. Pat. No. 5,591,166 discloses an orthopedic bone bolt and bone plateconstruction including a bone plate member and a collection offasteners. At least one of the fasteners allows for multi-angle mountingconfigurations. The fasteners also include threaded portions configuredto engage a patient's bone tissue.

U.S. Pat. No. 5,569,247 discloses a multi-angle fastener usable forconnecting patient bone to other surgical implant components. The '247device includes fastening bolts having spherical, multi-piece heads thatallow for adjustment during installation of the device.

U.S. Pat. No. 5,716,357 discloses a spinal treatment and long bonefixation apparatus. The apparatus includes link members adapted toengage patient vertebrae. The link members may be attached in achain-like fashion to connect bones in a non-linear arrangement. Theapparatus also includes at least one multi-directional attachment memberfor joining the link members. This allows the apparatus to be used informing a spinal implant fixation system.

Another type of spinal fixation system includes rigid screws that engagethe posterior region of a patient's spine. The screws are designed withrod-engaging free ends to engage a support rod that has been formed intoa desired spine-curvature-correcting orientation. Clamping members areoften used to lock the rod in place with respect to the screws. Insteadof clamping members, other fixation systems, such as that disclosed inU.S. Pat. No. 5,129,900, employ connectors that join the support rodsand anchoring screws. The connectors eliminate unwanted relative motionbetween the rod and the screws, thereby maintaining the patient's spinein a corrected orientation.

Other spinal fixation systems employ adjustable components. For example,U.S. Pat. No. 5,549,608 includes anchoring screws that have pivotingfree ends which attach to discrete rod-engaging couplers. As a result,the relative position of the anchoring screws and rods may be adjustedto achieve a proper fit, even after the screw has been anchored into apatient's spinal bone. This type of fixation system succeeds in easingthe rod-and-screw-linking process. This adjustment capability allows thescrews to accommodate several rod paths.

U.S. Pat. No. 7,445,627 discloses a fastener and a bone fixationassembly for internal fixation of vertebral bodies. According to oneexemplary embodiment, a tulip assembly is employed, the tulip assemblyincludes a non-circular surface disposed on its outer surface. Afastener is coupled to the tulip assembly and positionable to retain thetulip assembly on the head of a screw. A cap having an outer surface anda plurality of inner protrusions mateably connects to the non-circularsurface on the tulip body to compress the tulip assembly to secure arod.

U.S. Publication No. 2008/0177322 discloses a spinal stabilizationsystem that includes bone fastener assemblies that are coupled tovertebrae. Each bone fastener assembly includes a bone fastener and acollar. The bone fastener has a head portion having at least a firstcross-sectional shape in a first plane, and a second cross-sectionalshape in a second plane. The collar has a circular opening in thebottom, with a relief extending from the circular opening. The secondcross-sectional shape of the bone fastener is keyed to the opening topermit insertion of the bone fastener into the collar assembly from thebottom. After insertion, the bone fastener is rotated to prohibitremoval of the bone fastener from the collar. The collar can then berotated and/or angulated relative to the bone fastener. An elongatedmember can be positioned in the collar and a closure member is then usedto secure the elongated member to the collar.

U.S. Publication No. 2006/0241599 discloses a polyaxial fixation devicehaving a shank with a spherical head formed on a proximal end thereof,and a receiver member having an axial passage formed therein that isadapted to polyaxially seat the spherical head of the shank. Thepolyaxial bone screw further includes an engagement member that isadapted to provide sufficient friction between the spherical head andthe receiver member to enable the shank to be maintained in a desiredangular orientation before locking the spherical head within thereceiver member.

U.S. Publication No. 2006/0235392 discloses a system for connecting afastener element (e.g., a pedicle screw) relative to a rod for thepurposes of vertebral fixation. The system may permit multi-axialmovement between the fastener element and the rod. Further, the systemmay permit the angular relationship between the fastener element and therod to be held in a desired orientation.

U.S. Publication No. 2006/0155277 discloses an anchoring element forsecuring a rod on a vertebra, that comprises a retaining means forreceiving the rod, a safety element placed on the retaining means, asecuring element which can be placed on the body of the vertebra, and aclamping device which is arranged between the retaining means and thesecuring element. The clamping device includes a ring-shaped mount, apartially conical-segment shaped bearing and an intermediate elementwhich is embedded in the mount and which engages the bearing, wherebythe mounting is moveable in a removed state in relation to the bearing,whereas the mount is maintained in a clamped state on the bearing bymeans of the intermediate element. The mount is rigidly connected to theretaining means and the bearing is rigidly connected to the securingelement.

U.S. Publication No. 2006/0149240 discloses a polyaxial bone screwassembly that includes a threaded shank body having an upper capturestructure, a head and a multi-piece retainer, articulation structure.The geometry of the retainer structure pieces correspond and cooperatewith the external geometry of the capture structure to frictionallyenvelope the retainer structure between the capture structure and aninternal surface defining a cavity of the head. The head has a U-shapedcradle defining a channel for receiving a spinal fixation orstabilization longitudinal connecting member. The head channelcommunicates with the cavity and further with a restrictive opening thatreceives retainer pieces and the capture structure into the head butprevents passage of frictionally engaged retainer and capture structuresout of the head. The retainer structure includes a substantiallyspherical surface that mates with the internal surface of the head,providing a ball joint, enabling the head to be disposed at an anglerelative to the shank body.

U.S. Pat No. 6,716,214 discloses a polyaxial bone screw having a boneimplantable shank, a head and a retaining ring. The retaining ringincludes an outer partial hemispherical surface and an inner bore withradially extending channels and partial capture recesses. The shankincludes a bone implantable body with an external helical wound threadand an upwardly extending capture structure. The capture structureincludes at least one spline which extends radially outward and has awedged surface that faces radially outward therefrom. The capturestructure operably passes through a central bore of the retaining ringwhile the spline passes through a suitably shaped channel so that thespline becomes positioned above the head, at which time the shank isrotated appropriately and the shank is drawn back downwardly so that thespline engages and seats in the capture recess. The head includes aninternal cavity having a spherical shaped surface that mates with thering surface and has a lower restrictive neck that prevents passage ofthe ring once the ring is seated in the cavity.

U.S. Pat. No. 6,565,567 discloses a pedicle screw assembly for use witha rod for the immobilization of bone segments. The assembly is comprisedof a screw, a polyaxial housing for receiving the screw, a washer, a setscrew, and a cup-shaped cap. The lower portion of the housing terminatesin a reduced cross-sectional area, which engages the bottom of the screwhead. When the screw is placed inside the polyaxial housing and thescrew is secured into the bone, the polyaxial housing is pivotable withthree degrees of freedom. The housing includes a top portion with a pairof upstanding internally threaded posts. A washer is inserted betweenthe head of the screw and the rod. A cap, having a bottom, with a pairof posts accommodating openings and a lateral cross connector, is placedover the posts so that the cross connector engages the rod. The crossconnector and washer have concave generally semi-cylindrical rodengaging surfaces to prevent the rod from rotating or sliding within thehousing once the set screw is tightened. A set screw is threaded intothe housing posts to secure the rod within the housing. The washer has aroughened lower surface which, in conjunction with the reducedcross-sectional area at the bottom of the housing, securely clamps andlocks the housing to the screw head when the set screw is tightened.

U.S. Pat. No. 5,501,684 discloses an osteosynthetic fixation devicewhich consists of a fixation element which has a conical head sectionand an anchoring element abutting it which is for attachment into thebone. The fixation device also consists of a spherically formed,layered, slotted clamping piece which has a conical borehole forinstallation of the conical head section, and which is meant for lockingwithin a connecting piece equipped with a spherically shaped layeredborehole. Fixation piece has an axially arrayed tension element,permitting axial displacement and wedging of conical head section in theborehole that corresponds with it. The fixation device is appropriatefor use as a plate/screw system, an internal or external fixator, and inparticular for spinal column fixation.

U.S. Pat. No. 4,693,240 discloses a bone pin clamp for external fracturefixation. The apparatus comprises rotation, slide and housing elementsnested one within the next, each such element having an aperture toreceive a pin therethrough, and the rotation and slide elementsrespectively affording pin adjustment in azimuth and zenith, and inheight, relative to the housing element. A locking mechanism including acommon actuator member is operable simultaneously to lock the pin androtation and slide elements in the housing element. In a preferred form,the housing element serves as a cylinder with the slide element as akeyed piston therein, and the rotation element is a disc located betweena screw and annular thrust members engaged in the piston, the piston anddisc being split respectively to lock by expansion and compaction underscrew action towards the thrust members.

U.S. Pat. No. 4,483,334 discloses an external fixation device forholding bone segments in known relation to each other. The deviceincludes a pair of bone clamp assemblies each secured to bone pinsextending from the bone segments, a bridge extending between the pinclamp assemblies, and a specialized high friction universal assemblyconnecting the bridge to each of the pin clamp assemblies.

U.S. Pat. No. 4,273,116 discloses an external fixation device forreducing fractures and realigning bones that includes sliding universalarticulated couplings for enabling easy adjustment and subsequentlocking of connections between Steinmann pins and tubular tie-rods. Thecouplings each include a split, spherical adapter sleeve which isembraced by the matching inner surface of an open ring portion of acoupling locking clamp having clamp lugs tightenable against a block bymeans of a nut-and-bolt assembly. Further nut-and-bolt assemblies aredisposed in elongated slots in the blocks and cooperate with associatedclamping members to clamp the Steinmann pins to the blocks afteradjustment in two orthogonal directions and optional resilient bendingof the pins.

U.S. Pat. No. 6,672,788 discloses a ball and socket joint incorporatinga detent mechanism that provides positive biasing toward a desiredposition. The ball and socket joint can be used in flexible supportsthat hold and support items such as lamps, tools and faucets. The detentmechanism comprises two corresponding parts, one in the ball portion andthe second in the socket portion of the joint. The first detent part isa protrusion of some type and the second detent part is a groove orindentation that is adapted to accept and engage the protrusion. If theball contains the detent protrusion, then the socket contains the detentindentation. And conversely, if the socket contains the detentprotrusion, then the ball contains the detent indentation. The detenttensioning force can be provided by a spring or a spring band, thecharacteristics of the material from which the joint is made, or by someother similar tensioning device.

U.S. Publication No. 2003/0118395 discloses a ball and socket joint,which has a housing, a ball pivot mounted pivotably in the housing, anda sealing bellows, which is fastened to the housing and is mounted onthe ball pivot slidably via a sealing ring provided with two legs. Afirst leg of the two legs is in contact with the ball pivot undertension and the second leg meshes with the wall of the sealing bellows.The second leg is, furthermore, fastened in an anchoring ring arrangedat least partially in the wall of the sealing bellows.

U.S. Pat. No. 4,708,510 discloses a ball joint coupling assembly thatpermits universal movement and positioning of an object with respect toa vertical support shaft. Quick release/lock action is provided by aball joint assembly having a housing in which a ball and piston aremovably coupled. The ball is captured between annular jaw portions ofthe housing and piston, with locking action being provided by grippingengagement of the piston jaw portion and the housing jaw portion. Theball member is gripped in line-contact, compressive engagement by theannular edges of the piston jaw and housing jaw on opposite sides of theball. The piston is constrained for axial movement within the housingwith locking engagement and release being effected by rotation of athreaded actuator shaft.

U.S. Pat. No. 3,433,510 discloses a swivel structure for rigidly joiningfirst and second parts together. A first member is connected to thefirst part and a second member is connected to the second part. Anintermediate hollow member interconnects the first and second memberstogether. An enlarged outer end portion is provided on the first memberand includes a plurality of locking means thereon. Means are provided onthe second member for engaging one of the locking means. Means areprovided for threadably joining the hollow member and the second membertogether. A slot is provided in the hollow member and includes anenlarged entrance which passes the enlarged outer end portion and whichalso includes a restricted opening opposite the threaded joining of thehollow member and the second member together. The portion surroundingthe restricted opening opposes the forces imparted against the outer endportion as the second member is threadably joined to the hollow portionand bears against the outer end portion.

U.S. Patent Publication No. 2008/0269809 discloses a bottom loadingpedicle screw assembly. The device includes a pedicle screw and aconnector member. The pedicle screw includes a threaded lower portionwhile the upper portion includes a groove sized to accept a clip member.The clip member includes a spherical outer surface. In operation theclip is placed within the groove and the assembly is pressed through theopening in the bottom of the connector member. While the device isbottom loading, the device will separate when the pedicle screw isaligned with the connector member. The construction of the clip memberallows the clip to collapse sufficiently to pass back through theopening when the screw is positioned in alignment with the connector,requiring the connection to bone be placed at an angle with respect tothe connector for proper operation.

Thus, what is needed is a lockable polyaxial ball and socket joint thatcan be adapted for use in a spinal fixation system that includes theadvantages of known devices, while addressing the shortcomings that theyexhibit. The system should allow component interchangeability at pointof installation, thereby addressing a wide variety of spinal deformitieswith less components. In addition, the system should allow thestabilized angular placement position of the connector components duringinstallation. The connector component should be stabilized prior toconnection to a connecting rod so that the component will not flop overafter being positioned by the surgeon thereby enabling the surgeon toproperly align multiple components and configure the connecting rod tomatch the locations of the anchoring screws.

SUMMARY OF THE INVENTION

Briefly, the present invention is a polyaxial ball and socket jointcapable of snap together assembly and thereafter lockable into a fixedposition. Disclosed is an exemplary embodiment of the ball and socketfastening system adapted for use in a spinal fixation system forreshaping the spine of a patient. The fixation system includes thepolyaxial ball having a bone screw extending outwardly therefrom for usein anchoring to the spine and a connector member that includes a socketconstructed and arranged to accept the polyaxial ball. In the disclosedembodiment, the connector member is illustrated as a U-shaped connectormember having a lower receptacle that operates as a socket for housingan upper retainer ring and a lower split retaining ring. The socket isreceptive to the spherical connector which is inserted through anaperture in the bottom of the connector assembly where the sphericalpolyaxial ball contacts the lower split retainer ring causing amomentary displacement thereof, allowing the ring to contact a pluralityof ramps that are constructed and arranged to open the split ringallowing the ball to pass through the ring positioning of the sphericalconnector between the upper and lower retainer rings.

A set screw or nut can then be utilized to press the upper retainingring into contact with the ball while simultaneously causing the lowersplit ring to engage a lower portion of the ball as it wedges betweenthe ball and the inner surface of the connector member immobilizing theconnection.

This construction facilitates the receipt of the spherical connectorinto the bottom of the connector member, eliminating the requirement ofinserting the screw and spherical connector through the top opening ofthe connector member. This construction also allows for the use of boneanchors that will not fit through the top opening of the connectormember. In addition, the use of the dual retainer rings allows for thecoupling of an anchor screw to a connector member during surgery,without the aid of tools. In this manner, during surgery a surgeon candetermine the most advantageous bone screw, hook or other type of boneconnection to match the most advantageous connecting assembly. The boneconnector is then coupled to the connector assembly by inserting orsnapping the spherical connector into the socket of the connectingassembly. In operation, the spherical connector is pushed past the lowerretainer ring whereby the ring snaps past the largest diameter of theconnector to prohibit removal of the connector while still allowingpolyaxial movement between the spherical ball and the connector member.The upper retainer ring is resiliently biased against an upper componentof the connector member and engages the spherical ball so as to keep theU-shaped connector member in position during installation. A surgeon caneasily move the connector member into a preferred position and theresilient biasing component will keep sufficient force on the upperretainer ring so as to maintain the connector in a selected positionrelative to the spherical connector. This facilitates the installationof the rod as the U-shaped connector not only can be rotated into aposition for proper placement of the connecting rod but the proper angleof the saddle can also maintained while allowing the surgeon to alignadditional screws for ease of rod placement. In addition, by maintainingthe pre positioning of the connector members the surgeon will be able topre position and bend the rod as needed to align for any number ofanchoring screws. Because of the flexibility and resilience of the splitretention ring, the mating parts do not require fine tolerances and areeconomical to manufacture. The system is modular, employing a collectionof anchoring assemblies that are linked, via various connectors, tostrategically-arranged stabilizing rods.

The connector members are rigid structures adapted to link an associatedanchoring assembly with one of the stabilizing rods. The stabilizingrods may be rigid or dynamic members shaped to form aspine-curvature-correcting and/or immobilizing path. Attaching eachanchoring assembly, via connectors, to a stabilizing rod forces apatient's back into a surgeon-chosen shape. Stabilizing rods may be usedsingly, or in pairs, depending upon the type of correction required. Therods vary in size, but typically extend between at least two vertebrae.

Accordingly, it is an objective of the present invention to teach theuse of a lockable polyaxial ball and socket fastener.

It is another objective of the present invention to disclose the use ofa lockable polyaxial ball and socket fastener for use in a spinalstabilization system.

Another objective of the invention is to disclose the use of a lockablepolyaxial ball and socket system that is capable of securing variousanchors to various connector members so as to reduce the amount ofinventory required to meet a particular installation.

It is another objective of the present invention to provide a polyaxialbone screw assembly for a spinal fixation system that permits componentadjustment during installation, thereby enabling satisfactory correctionof a wide variety of spinal deformities.

It is an additional objective of the present invention to provide a bonescrew assembly that includes a split ring locking mechanism that issimple, stong and reliable.

It is yet another objective of the present invention to provide apolyaxial bone screw that can be coupled to a reciprocal connectingmember without tools.

It is yet another objective of the present invention to provide a spinalfixation system that require minimum tools for installing of an anchorand securing element.

Other objectives and advantages of this invention will become apparentfrom the following description taken in conjunction with theaccompanying drawings wherein are set forth, by way of illustration andexample, certain embodiments of this invention. The drawings constitutea part of this specification and include exemplary embodiments of thepresent invention and illustrate various objects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top perspective view of the ball and socket fastener appliedto a spinal fixation device;

FIG. 2 is a top perspective view of the ball and socket fastener withthe anchoring member illustrating the polyaxial cooperation between thespherical ball and the connector member;

FIG. 3 is a side view of the ball and socket fastener;

FIG. 4 is a partial section view of the ball and socket fastener;

FIG. 5 is a section view of the connector assembly;

FIG. 6 is a top section view of the connector assembly;

FIG. 7 is a perspective section view of the connector assembly takenalong lines 7-7 of FIG. 6;

FIG. 8 is a top perspective view of the connector assembly;

FIG. 9 is a top view of the connector assembly;

FIG. 10 is a section view of the connecter assembly taken along lines10-10 of FIG. 9;

FIG. 11 is a partial bottom perspective view of the connector member;

FIG. 12 is a partial top perspective view of the connector member;

FIG. 13 is a bottom view of the connector member;

FIG. 14 is a top perspective view of the seat portion of the connectormember;

FIG. 15 is a perspective view of the lower split retaining ring;

FIG. 16 is a perspective view illustrating the seat portion and thelower retaining ring;

FIG. 17 is a top perspective view of the upper retaining ring;

FIG. 18 is a lower perspective view of the upper retaining ring;

FIG. 19 is a perspective view illustrating assembly of the connectorassembly to the spherical connector;

FIG. 20A is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 20B is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 20C is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 20D is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 20E is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 20F is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 20G is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 20H is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 21A is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 21B is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 21C is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 21D is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 21E is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 21F is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 21G is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 21H is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 22 is a perspective view of an alternative embodiment of theinstant invention;

FIG. 23 is a partial side view of the embodiment illustrated in FIG. 22;

FIG. 24 is a top view of the embodiment illustrated in FIG. 22;

FIG. 25 is a perspective view of a retaining nut;

FIG. 26 is a perspective view of an alternative embodiment of theinstant invention having only mono-axial movement;

FIG. 27 is a front view of the bone anchor of the embodiment illustratedin FIG. 26;

FIG. 28 is a side view of the bone anchor of the embodiment illustratedin FIG. 26;

FIG. 29 is a partial perspective view of the spherical connectorutilized in the mono-axial embodiment;

FIG. 30 is a partial section view of the connector assembly utilized inthe mono-axial embodiment;

FIG. 31 is a lower perspective view of the upper retaining ring utilizedin the mono-axial embodiment.

FIG. 32 is a perspective top view of an alternative embodiment for theupper retaining ring.

FIG. 33 is a perspective bottom view of the alternative embodiment forthe upper retaining ring.

FIG. 34 is a cross sectional side view of the ball and socket fastenerhaving the alternative upper retaining ring assembled with a spinalfixation device.

FIG. 35 is a perspective view illustrating assembly of the connectorassembly having the upper retaining ring of FIG. 32 to the sphericalconnector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

While the present invention is susceptible of embodiment in variousforms, there is shown in the drawings and will hereinafter be describeda presently preferred embodiment with the understanding that the presentdisclosure is to be considered an exemplification of the invention andis not intended to limit the invention to the specific embodimentsillustrated.

Referring generally to the Figures, disclosed is an exemplary embodimentof the locking polyaxial ball and socket fastening system adapted foruse in a spinal fixation system. The fastening system includes aspherical ball secured or formed integrally with a bone anchor andconnecting assembly that includes a snap-in type receptacle (38) for thespherical ball to form a polyaxial joint. The connector assembly alsoincludes a receiver that may be used in conjunction with a connectingrod member for securing at least two bone anchors together.

Referring to FIGS. 1-4 and 19, the bone anchor of the preferredembodiment is a bone screw (12) including a shank (14) having a lengthwith at least one helical thread (16) formed along the length thereof.It is important to note that the proportions of the bone screw depictedare for illustrative purposes only and variations in the length of theshank, diameter of the screw, thread pitch, thread length, number ofthread leads, shank induced compression and the like may be variedwithout departing from the scope of the invention. At the upper end (20)of the shank (14) is a ball shaped spherical connector (18) having apredetermined diameter (d) (FIG. 19). A driver receptacle (22) islocated along the upper end (20) of the spherical connector for use ininstalling the bone screw by use of driving tool. It should be notedthat the driving receptacle may be any shape, male or female, suitablefor cooperation with a driving tool to rotate the bone screw into itsfinal position.

Referring to FIGS. 1-16, the U-shaped connector assembly (30) isillustrated. The U-shaped connector assembly (30) includes an upperconnector member (31) (FIGS. 11-13), a lower connector member (33) (FIG.14), an upper retaining ring (42) and a lower split retaining ring (40)(FIG. 5). The upper connector member (31) includes a substantiallycircular side wall (32) divided by a pair of U-shaped openings formingan upstanding first side wall (34) and second side wall (36). The sidewalls preferably include a plurality of recessed flutes (90). The flutesare constructed and arranged to provide a gripping surface thatcooperates with a tool (not shown) to allow a physician to apply acounter torque to the connector member during tightening of the setscrew (80) (FIG. 1). In addition to the flutes a groove (91) is cutaround the perimeter of the upper connector member (31) for attachmentof an extender tube (not shown). Extender tubes are well known in theart of minimally invasive spinal procedures. The lower surface of theupper connector member (31) includes a plurality of ramps (94) that arepositioned to cooperate with the lower split retaining ring (40) duringassembly to open the lower split retaining ring (40)so that the majordiameter (d) (FIG. 19) of the ball shaped spherical connector (18) canpass through the lower retaining ring (40) (see FIGS. 21A-21H).

Referring to FIGS. 4-16, the upper connector member (31) preferablyincludes a shoulder (92) on the bottom surface thereof for location ofthe lower connector member (33). The lower connector member (33) alsoincludes a shoulder (96) that is constructed and arranged to cooperatewith shoulder (92) to maintain alignment of the two components. Thelower connector member (33) includes a substantially spherical shapedlower receptacle (38) housing a lower split retainer ring (40) and upperretainer ring (42). The retainer rings (40, 42) are placed within thelower receptacle (38) during the manufacturing process. The shoulders(92) and (96) are utilized to align the components, and the upper andlower connector members are then laser welded together to preventdislodgement of the retainer rings after assembly. It should be notedthat other suitable methods or techniques of attaching the upper andlower connector members together may be utilized without departing fromthe scope of the invention, such methods may include, but should not belimited to spot welding, threads, adhesives, pins swaging, solder,interference fits and suitable combinations thereof.

Referring to FIGS. 5-13 and 17-18, the upper retainer ring (42) isillustrated. The upper retaining ring (42) is positioned within thelower receptacle (38) with an upper edge (52) positionable within thecavity formed by side wall (41); the upper retaining ring side wall (43)cooperates with side wall (41) of the cavity to prevent rotation of theupper retaining ring (42). The inner surface (56) of the upper retainingring (42) provides for self centering by engaging of the outer surfaceof the spherical connector (18). The upper surface (53) of the upperretaining ring (104) preferably includes a concave cylindrical surfacefor cooperation with the connecting rod (70). The cylindrical surfaceprovides additional surface area for contact with the connecting rod(70) and may include a knurled or otherwise modified surface finishadapted to enhance gripping power between the rod (70) and theconnecting assembly (30). The upper cylindrical surface (53) includes anaperture to facilitate access to the driver receptacle (22). Theconnector assembly (30) has a longitudinal axis L1.

In one embodiment the upper retaining ring (42) includes spring pockets(98) that are in alignment with and located to cooperate with springpockets (100) (FIG. 11) positioned in the upper connector member tolocate and contain coil springs (102) (FIG. 5). The spring pockets(98,100) each have a longitudinal axis L2 that is parallel to thelongitudinal axis L1 of the connector assembly (30). As shown in FIG. 5the springs (102) are in a compressed state wherein their length is lessthan when in their neutral or unbiased condition. The spring pockets(98) and (100) are generally cylindrical bores with a diametersufficiently large enough to receive springs (102). The axis of eachthese cylindrical bores are parallel to the longitudinal axis of theconnector assembly (30). The spring members (102) bias the upperretaining ring (42) toward the opening (50) of the lower receptacle(38). The springs (102) apply a substantially uniform downward forceupon the upper retaining ring (42) thereby maintaining the upperretaining ring (42) in a plane generally perpendicular to a plane thatincludes the longitudinal axis of the connector assembly (30). The ramps(94) located about the perimeter of the upper retainer ring (42) apply asubstantially uniform downward force about the perimeter of the lowerretaining ring (40). The application of this uniform biasing force onthe lower ring ensures that the lower retaining ring (40) will not bindas it passes over the lower portion of the spherical connector (18).After the spherical connector (18) has been captured by the lowerretaining ring (40) the springs (102) will thereafter serve to maintaina downward force on the upper retaining ring (42) that in turn producesa downward force on the spherical connector (18) which in turn is exertsa downward force of the lower retainer ring (40) that in turn exerts adownward force on the conical surface (39) formed on the inner surfaceof lower connector member (33). The downward biasing force created bythe springs creates a frictional engagement of the spherical connector(18) with the upper and lower retaining rings (40,42) as well as theconnector assembly (30).

Referring to FIGS. 19-21H, assembly of the locking polyaxial ball andsocket fastener is illustrated. Prior to assembly, the bone anchor (12)may be inserted into bone in a normal fashion without the connectormember attached thereto. This allows the physician to a clearvisualization of the screw as it is rotated into the bone. Afterinsertion of the bone screw, the spherical connector (18) of the boneanchor (12) is inserted through the opening (50) (FIG. 21A) wherein thespherical connector (18) contacts the lower retainer ring (40). Thelower retaining ring is pushed into contact with the upper retainingring (42) (FIG. 21B) thereby collapsing the springs (102) to cause thelower retaining ring (40) to contact the ramps 94 (FIG. 21C). Thecooperation of the ramps (94) with the upper surface of the lowerretaining ring (40) causes the lower retaining ring (40) to open up indiameter to snap over the major diameter (d) of the spherical connector(18) (FIGS. 21D-21F). Once the lower retainer ring (40) is openedsufficiently, the springs (102) move the lower retainer ring (40) to thelower portion of the lower connector member 33 thereby preventing thespherical connector (18) from being removed from the lower connectormember (31) while still allowing polyaxial movement of the connectorassembly (30) with respect to the screw (12) (FIGS. 21G-21H). Lockingthe ball and socket connection into a desired position is thereafteraccomplished by placing a connecting rod (70) into the connectorassembly (30) so that it contacts the upper surface (53) of the upperretaining ring (42). A securing element in the form of a set screw (80)is inserted into the threaded portion of the upper retaining member (31)until the set screw (80) contacts the rod (70), causing the rod (70) tomove the upper retaining ring (42) into contact with the sphericalconnector (18). The movement causes the spherical connector (18) to movetoward the opening (50), wedging the lower split retaining ring 40between the inner surface (120) (FIG. 14) of the lower retaining ring(40) and the spherical connector (18), locking the assembly in a desiredposition. The inner surface (54) of the lower retaining ring (40) isgenerally spherical in configuration and is complimentary to thespherical surface on the spherical connector (18). It should beappreciated that this construction provides two rings of contact betweenthe connector assembly (30) and the spherical ball connector. The firstring of contact is provided by the upper retaining ring (42) and thesecond ring of contact is provided by the lower retaining ring (40). Itshould be noted that while the springs (102) are illustrated as coilsprings, any spring or resilient type member suitable for displacing thesplit retaining ring may be utilized without departing from the scope ofthe invention. Such spring or resilient members may include, but shouldnot be limited to, Belleville type springs, leaf springs, polymericmembers and suitable combinations thereof.

Unique to this invention is the ability for the surgeon to attachvarious types of bone anchors or the like to the connecting assembly.While there is a myriad of anchoring devices that can be adapted toinclude the spherical ball, bone hooks etc., for ease of illustrationthe bone screw is depicted and it is well known that various lengths anddiameters of bone screws are available, many of which would not fitthrough the inner diameter of the connector assembly. Thread styles,lengths and so forth the best suited for installation may be estimatedbefore surgery but it is well known that only during actual surgery canthe proper style be confirmed. Because it is most difficult to predictthe proper combination of anchor screw and connector member, surgeonsmust either have a large selection of spinal implants to choose from orbe forced to use the closest combination and hope that it will suffice.

It should be noted that while various types of bone screws have beenmentioned, the instant installation allows placement of an anchoringdevice having a spherical connector into position before a connectormember is attached. This provides the surgeon with an option ofpositioning the bone screw before placement of the connecting memberthereby providing a simplified installation should positioning of theanchoring screw be difficult due to muscle or other interference.Installation of a bone screw with the connecting member allows a rangeof mobility as well as better visual positioning. Further, while theU-shaped connector member is depicted, various types of connectormembers may be used in combination with the spherical connector (18)allowing a surgeon to select the appropriate combination during surgerythereby enhancing the success for the benefit of the patient as well aslowering cost of inventory necessary when estimating the various typesof situations that the surgeon may encounter during the operation.

It should also be noted that while only the lower retaining ring isillustrated as being split, the upper ring may also be split tofacilitate placement into the lower receptacle without the need to weldthe upper and lower portions of the retainer assembly together.

Referring to FIG. 19, the outer surface (83) of the spherical connector(18) may include a ridged style surface for enhanced frictionalengagement. It should also be noted that the spherical connector ispreferably sized only for insertion through the bottom opening (50) ofthe connector assembly (31) and would not fit through the connectormember opening (80) even if the upper retainer ring (42) was removed.This entry is a departure from conventional prior art which typicallyplaces the shank of a bone screw through the connector member whereinthe opening along the bottom of the connector is sized to preventpassage of the spherical connector.

Referring to FIGS. 4 and 19, the fastener receptacle (22) can be made ofvarious shapes with the emphasis of providing a shank or a conventionalfastener tool that provides the greatest amount of torque with minimalamount of slippage during installation. The inner surface (54) (FIGS.15-16) of the lower retainer ring (40) is shown with a minimal portionof the surface engaging the spherical connector (18) duringinstallation. However, once the spherical connector is positioned, themajority of the inner surface (54) of the lower split retaining ring(40) will engage the spherical connector (18) for optimal frictionengagement. Similarly, the inner surface (56) of the upper retainer ring(42) (FIG. 18) engages the spherical connector (18) for frictionalengagement. Preferably the inner surfaces (54 and 56) include a ridgedsurface that cooperates with the ridged surface (83) of the sphericalconnector (18).

Referring to FIGS. 22-25, an alternative embodiment of the instantinvention is illustrated. In this embodiment, the set screw (80) isreplaced by a threaded nut (110). The threaded nut includes internalhelical threads constructed and arranged to cooperate with externalthreads (112) formed on the outer surface of the upper connector member(31). The threaded nut (110) includes a bottom surface (114) thatengages the rod member (70), thereby causing the upper retainer member(42) to engage the spherical connector (18) to wedge the lower retainingring (40) between the spherical connector and the inner surface (120) ofthe lower connector member (33) to lock the position of the sphericalconnector with respect to the connector assembly. The surface (120) onthe lower connector member (33) is generally conical and conforms to theconical surface (39) formed on the outer surface of the lower retainingring (40).

Referring to FIGS. 26-31, an alternative embodiment of the instantinvention is illustrated having mono-axial movement (see FIG. 26) inplace of the polyaxial movement of the embodiments described above. Boneanchors that provide mono-axial movement, e.g. along a single axis,instead of polyaxial movement, e.g. motion along several different axes,are often desired for certain types of the spinal ailments such as, butnot limited to, scoliosis. To limit the movement of the ball and socketfastener to a single axis, the spherical connector (18) includes, atleast one, and more preferably a pair of guide(s) surface(s) (116)positioned on opposite side sides of the spherical connector (18) (FIG.27). The guide surfaces (116) cooperate with rails (118) positionedwithin the inner surface (56) of the upper retaining ring (42). Therails (118) and the guide surfaces (116) cooperate to preventsubstantial rotation of the spherical connector (18) while allowingmovement of the bone anchor (12) along a single axis (FIG. 26).

FIGS. 32 through 35 illustrate the ball and socket connector having analternative embodiment for the upper retainer ring. In this embodimentthe upper retainer ring (142) includes a continuous bearing surface(153) having a concave cylindrical surface for cooperation with theconnecting rod (70). The continuous cylindrical surface (153) providesadditional surface area for contact with the connecting rod (70) and mayinclude a knurled or otherwise modified surface finish adapted toenhance gripping power between the rod (70) and the connecting assembly(30). The outer surface (83) of the spherical connector (18) may includea ridged style surface for enhanced frictional engagement. A driverreceptacle (22) is located along the upper end of the sphericalconnector (18) for use in installing the bone screw by use of drivingtool. The upper retaining ring (142) includes spring pockets (98) thatare in alignment with and located to cooperate with spring pockets (100)(FIG. 34) positioned in the upper connector member to locate and containcoil springs (102). A securing element in the form of a set screw (80)is inserted into the threaded portion of the upper retaining memberuntil the set screw (80) contacts the rod (70), causing the rod (70) tomove the upper retaining ring (142) into contact with the sphericalconnector (18). The rails (118) could likewise be incorporated into theupper retaining ring (142) for cooperation with guide surfaces (116) asdisclosed above with respect to FIGS. 26 through 30.

All patents and publications mentioned in this specification areindicative of the levels of those skilled in the art to which theinvention pertains. All patents and publications are herein incorporatedby reference to the same extent as if each individual publication wasspecifically and individually indicated to be incorporated by reference.

It is to be understood that while a certain form of the invention isillustrated, it is not to be limited to the specific form or arrangementherein described and shown. It will be apparent to those skilled in theart that various changes may be made without departing from the scope ofthe invention and the invention is not to be considered limited to whatis shown and described in the specification and any drawings/figuresincluded herein.

One skilled in the art will readily appreciate that the presentinvention is well adapted to carry out the objectives and obtain theends and advantages mentioned, as well as those inherent therein. Theembodiments, methods, procedures and techniques described herein arepresently representative of the preferred embodiments, are intended tobe exemplary and are not intended as limitations on the scope. Changestherein and other uses will occur to those skilled in the art which areencompassed within the spirit of the invention and are defined by thescope of the appended claims. Although the invention has been describedin connection with specific preferred embodiments, it should beunderstood that the invention as claimed should not be unduly limited tosuch specific embodiments. Indeed, various modifications of thedescribed modes for carrying out the invention which are obvious tothose skilled in the art are intended to be within the scope of thefollowing claims.

1. A ball and socket fastener comprising: an anchoring member having ashank and a spherical connector; a connecting assembly having a socketconstructed and arranged for receipt of said spherical connector withina first end of said connecting assembly and a securing element securableto a second end of said connecting assembly, an upper retainer ringdisposed within said socket and positionable along an upper surface ofsaid spherical connector, a bearing surface operatively engaging a lowersurface of said spherical connector so that said connecting assemblymoves polyaxially with respect to said anchoring member, a resilientcomponent positioned between said connecting assembly and said upperretaining member, said resilient component having a first length in aunbiased state and a second shorter length in a compressed state, saidresilient component in said compressed state exerting a force upon saidupper retaining ring that in turn exerts a force upon the sphericalconnector which in turn exerts a force upon said bearing surface that isin cooperative engagement with said lower portion of said sphericalconnector, wherein said connecting assembly can be moved into apredetermined position relative to said spherical connector and maintainsaid predetermined relative position under the force exerted by saidresilient component, said securing element traversable between anunlocked position and a locked position for controlling said polyaxialmovement.
 2. The ball and socket fastener of claim 1 wherein saidresilient component includes at least one spring element, said springelement having a longitudinal axis that is parallel to a longitudinalaxis of said connecting assembly.
 3. The ball and socket fastener ofclaim 1 wherein the length of said resilient component in both saidfirst and second state is greater than a cross sectional width of saidresilient member.
 4. The ball and socket fastener of claim 1 whereinsaid resilient component is comprised of a plurality of discreteelements.
 5. The ball and socket fastener of claim 4 wherein each ofsaid discrete elements is a coil spring.
 6. The ball and socket fastenerof claim 5 wherein said connector assembly includes a plurality ofpockets in the form of cylindrical bores that are located within theside wall of the connector assembly, each of said bores having alongitudinal axis that extends parallel to the longitudinal axis of theconnector assembly, wherein each bore is sized and configured to receiveone of said discrete elements.
 7. The ball and socket fastener of claim5 wherein said upper retaining member includes a plurality of pockets inthe form of cylindrical bores, each of said cylindrical bores withinsaid upper retaining member having a longitudinal axis that extendsparallel to the longitudinal axis of said connector assembly, whereineach of said cylindrical bores within said upper retaining member issized and configured to receive one of said discrete elements.
 8. Theball and socket fastener of claim 6 wherein said upper retaining memberincludes a plurality of pockets in the form of cylindrical bores, eachof said cylindrical bores within said upper retaining member having alongitudinal axis that extends parallel to the longitudinal axis of saidconnector assembly, wherein each of said cylindrical bores within saidupper retaining member is sized and configured to receive one of saiddiscrete elements.
 9. The ball and socket fastener of claim 5 whereinsaid discrete elements are two coil springs.
 10. The ball and socketfastener of claim 1 wherein said bearing surface includes a lower ring.11. The ball and socket fastener of claim 10 wherein said lower ring isa retaining ring positioned between said spherical connector and saidconnector assembly.
 12. The ball and socket fastener of claim 11 whereinsaid lower retainer ring includes a split to allow said lower retainerring to expand in diameter.
 13. The ball and socket fastener of claim 1wherein said connecting assembly includes a substantially U-shapedopening sized to accept a rod member, an upper surface of said upperretaining ring including a rod engaging surface extending into saidU-shaped opening, wherein said locked position of said securing elementtraverses said upper retainer ring to frictionally engage said sphericalconnector.
 14. The ball and socket fastener of claim 13 wherein saidupper retaining ring includes a cylindrically concave upper surface forcooperation with a connecting rod member.
 15. The ball and socketfastener of claim 13 wherein said locked position causes said lowerretaining ring to engage an inner surface of said connector and saidlower portion of said spherical connector to immobilize said sphericalconnector.
 16. The ball and socket fastener of claim 1 wherein saidsecond end of said connecting assembly includes an internal thread andsaid securing element is further defined as a set screw.
 17. The balland socket fastener of claim 1 wherein said second end of saidconnecting assembly includes an external thread and said securingelement is further defined as a nut having internal threads.
 18. Theball and socket fastener of claim 14 wherein said cylindrically concaveupper surface includes a centrally located aperture.
 19. The ball andsocket fastener of claim 14 wherein said cylindrically concave uppersurface is continuous throughout its length and width.
 20. A ball andsocket fastener comprising: an anchoring member having a shank and aspherical connector including at least one guide surface; a connectingassembly having a socket constructed and arranged for receipt of saidspherical connector within a first end of said connecting assembly and asecuring element securable to a second end of said connecting assembly,an upper retainer ring disposed within said socket and positionablealong an upper surface of said spherical connector, said upper retainingring including at least one rail positioned to cooperate with said atleast one guide surface, a bearing surface operatively engaging a lowersurface of said spherical connector so that said connecting assemblymoves polyaxially with respect to said anchoring member, a resilientcomponent positioned between said connecting assembly and said upperretaining member, said resilient component having a first length in aunbiased state and a second shorter length in a compressed state, saidresilient component in said compressed state exerting a force upon saidupper retaining ring that in turn exerts a force upon the sphericalconnector which in turn exerts a force upon said bearing surface that isin cooperative engagement with said lower portion of said sphericalconnector, wherein said connecting assembly can be moved into apredetermined position relative to said spherical connector and maintainsaid predetermined relative position under the force exerted by saidresilient component, said at least one guide surface and said at leastone rail cooperating so that said connecting assembly moves mono-axiallywith respect to said anchoring member, said securing element traversablebetween an unlocked position and a locked position for controlling saidpolyaxial movement.
 21. The ball and socket fastener of claim 20 whereinsaid resilient component includes at least one spring element, saidspring element having a longitudinal axis that is parallel to alongitudinal axis of said connecting assembly.
 22. The ball and socketfastener of claim 20 wherein the length of said resilient component inboth said first and second state is greater than a cross sectional widthof said resilient member.
 23. The ball and socket fastener of claim 20wherein said resilient component is comprised of a plurality of discreteelements.
 24. The ball and socket fastener of claim 23 wherein each ofsaid discrete elements is a coil spring.
 25. The ball and socketfastener of claim 24 wherein said connector assembly includes aplurality of pockets in the form of cylindrical bores that are locatedwithin the side wall of the connector assembly, each of said boreshaving a longitudinal axis that extends parallel to the longitudinalaxis of the connector assembly, wherein each bore is sized andconfigured to receive one of said discrete elements.
 26. The ball andsocket fastener of claim 25 wherein said upper retaining member includesa plurality of pockets in the form of cylindrical bores, each of saidcylindrical bores within said upper retaining member having alongitudinal axis that extends parallel to the longitudinal axis of saidconnector assembly, wherein each of said cylindrical bores within saidupper retaining member is sized and configured to receive one of saiddiscrete elements.
 27. The ball and socket fastener of claim 25 whereinsaid upper retaining member includes a plurality of pockets in the formof cylindrical bores, each of said cylindrical bores within said upperretaining member having a longitudinal axis that extends parallel to thelongitudinal axis of said connector assembly, wherein each of saidcylindrical bores within said upper retaining member is sized andconfigured to receive one of said discrete elements.
 28. The ball andsocket fastener of claim 24 wherein said are discrete elements are twocoil springs.
 29. The ball and socket fastener of claim 20 wherein saidbearing surface includes a lower ring.
 30. The ball and socket fastenerof claim 29 wherein said lower ring is a retaining ring positionedbetween said spherical connector and said connector assembly.
 31. Theball and socket fastener of claim 30 wherein said lower retainer ringincludes a split to allow said lower retainer ring to expand indiameter.
 32. The ball and socket fastener of claim 20 wherein saidconnecting assembly includes a substantially U-shaped opening sized toaccept a rod member, an upper surface of said retaining ring including arod engaging surface extending into said U-shaped opening, wherein saidlocked position of said securing element traverses said upper retainerring to frictionally engage said spherical connector.
 33. The ball andsocket fastener of claim 32 wherein said upper retaining ring includes acylindrically concave upper surface for cooperation with a connectingrod member.
 34. The ball and socket fastener of claim 32 wherein saidlocked position causes said lower retaining ring to engage an innersurface of said connector and said lower portion of said sphericalconnector to immobilize said spherical connector.
 35. The ball andsocket fastener of claim 20 wherein said second end of said connectingassembly includes an internal thread and said securing element isfurther defined as a set screw.
 36. The ball and socket fastener ofclaim 20 wherein said second end of said connecting assembly includes anexternal thread and said securing element is further defined as a nuthaving internal threads.
 37. The ball and socket fastener of claim 33wherein said cylindrically concave upper surface includes a centrallylocated aperture.
 38. The ball and socket fastener of claim 33 whereinsaid cylindrically concave upper surface is continuous throughout itslength and width.